When you go to the gym do you see people move freely, unconstrained or stuck in a pattern of repeated movement? Human body completes task as a whole rather than individual muscle movement such as bicep curls or quads extension. When human body spreads forces and stress out into entire system including joints and tissues, it gets task done effectively with less injury. Try it at your next workout: change your position during exercise in three planes of motion, alternate your grip and variate speed and direction of your chosen loads.